The present invention relates to a double-chuck mechanical pencil provided with a feed chuck for feeding a lead, and a holding chuck for holding a lead.
Various double-chuck mechanical pencils intended to reduce the loss of leads have been proposed in recent years. Such a double-chuck mechanical pencil is provided with a feed chuck for feeding a lead and a holding chuck for holding a lead. The conventional double-chuck mechanical pencil is a complicated structure provided with a feed chuck mechanism and a holding chuck mechanism and, therefore, has the following problems.
If a barrel cap, which requires accurate machining, is found to be defective during the manufacture of a double-chuck mechanical pencil, it is difficult to replace the defective barrel cap with a good one because the double-chuck mechanical pencil has complicated construction and parts are supplied in units. Since the structural condition requires the parts to be assembled in a plurality of layers and hence the outside diameter of the internal mechanism of the double-chuck mechanical pencil is inevitably large, the double-chuck mechanical pencil cannot be formed in a small outside diameter.
When the user drops the double-chuck mechanical pencil inadvertently and the lead is broken in the chuck, the parts cannot be easily disassembled and it is difficult to remove the broken leads because the internal mechanism of the double-chuck mechanical pencil is a complete assembly of unit assemblies. If a conventional double-chuck mechanical pencil is dropped during transportation, a holding chuck placed in a barrel cap is deformed by shocks and becomes defective, and the lead is broken.
The present invention has been made to solve the foregoing problems in the conventional double-chuck mechanical pencils and it is therefore a first object of the present invention to provide a double-chuck mechanical pencil facilitating replacing a holding chuck found to be defective during a manufacturing process with a new one, and capable of being easily disassembled to remove broken leads when broken leads are jammed.
A second object of the present invention is to provide a double-chuck mechanical pencil including a barrel cap, a mechanical unit including a feed chuck, twisted in the barrel cap and fixed to the barrel cap by a stopper tube, and a front barrel which can be used in both a ballpoint pen and a mechanical pencil. The double-chuck mechanical pencil provided with the front barrel capable of being used in both a ballpoint pen and a mechanical pencil can be manufactured at a high productivity and facilitates process management.
A third object of the present invention is to provide a double-chuck mechanical pencil provided with a separate internal mechanism instead of a complete unit internal mechanism to reduce the eccentricity (thickness deviation) of molded parts including a sleeve bolster, a sleeve and a stopping tube, and facilitating aligning the axes of parts forming a lead passage.
When the foremost lead is worn out while a double-chuck mechanical pencil is used for writing and the next lead needs to be fed, it is desirable that a feed chuck is kept centered in a barrel as far as possible while the feed chuck feeds the next lead. For example, if the feed chuck is pressed obliquely in a lead tank or a high pressure that warps the lead tank is applied to the lead tank, the feed chuck vibrates to misalign the succeeding lead with the preceding lead and, consequently, the succeeding lead cannot be smoothly fed.
Accordingly, it is a third object of the present invention to provide a double-chuck mechanical pencil including a long barrel cap, a stopper tube disposed in a back part to reduce the bend of a lead tank when a pressure is applied to the lead tank and to reduce the vibration of a feed chuck, and capable of surely feeding a lead.
A fourth object of the present invention is to provide a double-chuck mechanical pencil having an internal mechanism formed in the least possible outside diameter, and formed in a small outside diameter.
A fifth object of the present invention is to provide a double-chuck mechanical pencil having a holding chuck placed in a barrel cap, and associated mechanisms. The holding chuck being capable of absorbing shocks and is resistant to deformation and hence leads are not easily broken.
According to one aspect of the present invention, a double-chuck mechanical pencil comprises: a barrel; a barrel cap attached to the front end of the barrel; a lead tank inserted in the barrel; a feed chuck for feeding leads, combined with the lead tank; a sleeve bolster disposed on the front side of the feed chuck; and a holding chuck combined with the sleeve bolster; wherein a holding chuck unit including the holding chuck and the sleeve bolster, and a feed chuck unit including the feed chuck and a sleeve can come into contact with each other in the barrel cap.
According to another aspect of the present invention, a double-chuck mechanical pencil comprises: a barrel; a barrel cap detachably attached to a front end of the barrel; a lead tank inserted in the barrel so as to be operated for longitudinal sliding in the barrel; a feed chuck directly or indirectly fixed to a front end of the lead tank; a chuck ring loosely put on the feed chuck; a sleeve interposed between the barrel cap and the feed chuck; a sleeve bolster in contact with a front end of the sleeve; a holding chuck fixed to the front end of the sleeve; a return spring interposed between the sleeve and the lead tank; a tip spring interposed between the barrel cap and the sleeve; a stopper tube surrounding the lead tank and engaged with a back end of the barrel cap.